Pygmy Allosaurus

Swampwalk on a green creature is a piece of color-pie geometry pointed exactly where it should be: black is the color that fills the board with Swamps, and landwalk is an offensive keyword designed to punish whoever plays the matching land type. The Ice Age cycle handed each color a walk aimed at a plausible enemy, and green attacking into black is a real matchup, which is the design logic that keeps this from being arbitrary. The trouble is the rate. Swampwalk only earns its keep when the defending player actually controls a Swamp, so the card's entire reason to exist is contingent on who sits across from it; against any other deck, this is effectively a 2/2 that costs more than a vanilla 2/2 should. Landwalk is the most conditional evasion Magic ever printed: nothing on an empty board, nothing against the wrong colors, and unblockable against exactly one opponent. That fragility is why the mechanic was eventually retired from main-set design in favor of always-on keywords like menace. What this represents, then, is a snapshot of an early-design instinct that has since been abandoned: build evasion around predicting your opponent's mana base rather than around the board you can see.